In general, the "disposable cleaning sheet" collects dust by making use of complicatedly entangled fibers on its surface, and during use is attached, for example, to a plate with a flat bottom face which is provided at the leading end of a cleaning mop.
In the above case of attaching the cleaning sheet to a mop in order to perform a wiping operation, a problem arises due to the flat bottom face of the plate. Specifically, the cleaning sheet can not readily collect the dust at its middle region, which covers the center of the bottom face of the plate while collecting the dust at its peripheral edge regions covering the edge portions of the plate. As a result, the entire cleaning sheet cannot be effectively exploited.
FIG. 8 is a side section showing a prior art cleaning sheet for eliminating the aforementioned defect while attached to a cleaning mop; FIG. 9 is a side section showing another prior art cleaning mop for eliminating the aforementioned defect while having a cleaning sheet attached thereto; and FIG. 10 is a side section showing the cleaning sheet of the prior art shown in FIG. 8 in actual use.
The cleaning sheet, as shown in FIG. 8, belongs to the same kind as that disclosed in Unexamined Published Japanese Patent Application No. 10-5163, for example. A sheet 31 is made thicker at its middle region 31a than the peripheral edge regions 31b and 31b. When this sheet 31 is attached to a cleaning mop M or the like, the middle region 31a is positioned at the central region of a plate Mp of the cleaning mop M. When a surface to be cleaned such as a floor is cleaned with that sheet 31, the middle region 31a comes into abutment against the surface to be cleaned while forming an indented space 32a between the peripheral edge region 31b and the surface to be cleaned. By moving the cleaning mop M along the surface to be cleaned to perform the wiping operation, a relatively large piece of dust can be collected in the indented space 32a to enhance the dust collecting effect.
In the prior art device shown in FIG. 9, unlike that shown in FIG. 8, the bottom face of the plate Mp of the cleaning mop M itself is formed into a bulging shape to form indented spaces 32b and 32b between a central portion M1 and edge portions M2 and M2, respectively. When the wiping operation is performed with the bottom face (including the central portion M1, the indented spaces 32b and the edge portions M2) of the cleaning mop M covered with a flat cleaning sheet (or a flat sheet) 31', the relatively large piece of dust can be collected in the indented spaces 32b.
However, the prior art thus far described suffers from the following problems. In the prior art shown in FIGS. 8 or 9, either the area of the middle region 31a of the cleaning sheet 31 or the area (i.e., the area of the cleaning sheet 31' in contact with the surface to be cleaned) of the central portion M1 of the cleaning mop M is smaller than the entire area of the bottom face of the cleaning mop M. As a result, the cleaning mop M is liable to become unstable with respect to the surface to be cleaned. For example, the frictional force acting upon the cleaning mop M when the cleaning mop M is moved in a direction X along the surface to be cleaned is liable to incline the plate Mp with respect to the surface to be cleaned, as shown in FIG. 10. In this state in which the plate Mp of the cleaning mop M takes the inclined position, the cleaning mop M cannot be smoothly moved with respect to the surface to be cleaned during the wiping operation.
In the aforementioned structure, furthermore, the dust collecting effect is enhanced by trapping a relatively large piece of dust in the indented spaces 32a or 32b. If the cleaning mop M is moved in the inclined position, however, an end of the peripheral edge portion 31b of the sheet 31, as shown in FIG. 8, or the edge portion M2 of the cleaning mop M, as shown in FIG. 9, comes into contact with the surface to be cleaned. As a result, the leading side of the indented space 32a or 32b in the direction of movement (i.e., the direction X) of the cleaning mop M becomes closed. This prevents the entrance of dust into the indented space 32a or 32b and raises the problem that the dust collecting effect is not sufficiently achieved.